Screening for gestational diabetes mellitus: the Sri Lankan experience.

OBJECTIVE: To evaluate tests used for screening and confirmation of gestational diabetes mellitus (GDM) in Sri Lanka. METHODS FIELD BASED: Consecutive pregnant women in Homagama DDHS area (n = 853), were assessed for risk factors and subjected to random and postprandial urinary Benedict's and Dipstick tests, fasting and 2 hour post 75 g glucose capillary blood glucose (FBG and 2hBG) which were validated against 75 g oral glucose tolerance test (OGTT) performed at 24-28 weeks (WHO criteria). HOSPITAL BASED: Retrospective analysis of consecutive high-risk women (n = 999) and prospective study of randomly selected GDM women (n = 66) to assess predictive value of the OGTT. RESULTS FIELD BASED: Sensitivity and specificity respectively of random urine Benedict's, 10%, 99.2%; postprandial urine Benedict's, 52.2%, 94.5%; postprandial urine Dipstick, 68.7%, 90%; capillary FBG threshold 4.1 mmol/l, 62.6%, 73%; capillary 2hBG threshold 7.2 mmol/l, 98.5%, 95.2%; risk factors, 93.1%, 22.2%. HOSPITAL BASED: OGTT-11.6% lag curves, 16.3% abnormal, FPG accuracy at 4.7mmol/l; predictive value of 2 hPG > or = 8.9 mmol/l for insulin treatment-sensitivity 97.2%, specificity 71.4%. CONCLUSIONS: Current practice of random urine testing in community screening for gestational diabetes is unreliable, and glucose specific postprandial urine test improves sensitivity. FPG is unsuitable for screening, the 2 hour post 75 g blood glucose at a threshold of > 7.2 mmol/l is sensitive and specific. In laboratory confirmation using 75 g OGTT the fasting plasma glucose has low predictive value, 2 hour test performed alone is liable to false positives and 2 hour glucose > 8.9 mmol/l following a peak at 1 hour suggests the need for insulin treatment.